Graft Versus Leukemia With Little Graft Versus Host Disease? Long Term Follow-Up Of a Study Using Transduced Donor T-Cells For Donor Leukocyte Transfusion

Fourteen patients with myeloid leukemia (12 with acute and 2 with chronic myelogenous leukemia) were transplanted from their HLA-identical (n = 9) or haploidentical (n = 5) family donors with CD34-enriched stem cells (HSCT) without further immunosuppression. In order to induce a graft versus leukemia (GvL) effect and to investigate the possibility of controlling graft-versus-host disease (GvHD), the standard transplantation protocol was adapted to include transfusion of gene-modified donor T-cells after HSCT in 11 patients, 3 did not receive any T-cells.

Donor-T-cells were transduced with the replication-deficient retrovirus SFCMM-3 which expresses the herpes simplex thymidine kinase (HSV-Tk) as a suicide gene and the truncated low affinity nerve growth factor receptor (ΔLNGFR) for selection purposes. After transfusion, SFCMM-3 transduced T-cells were detectable in all 11 patients by PCR and FACS analyses immediately after transfusion and during the follow up period (range: 1.1-11 years). Two of 9 patients developed acute GvHD: one of the skin, grade 1, 56 days after transfusion of the transduced cells, the other grade II which was successfully treated with ganciclovir. Loss of bcr-abl gene expression was achieved in one patient after expansion of transduced cells. Donor chimerism was stabilized after transfusion of transduced cells in all patients treated. In one patient a cytomegalovirus-reactivation was treated by the transfusion of gene-modified donor T-cells also indicating effectiveness of treatment. To date, 5 patients have relapsed, and died, one after a second HSCT. Two of the patients without transduced T-cells died due to relapse and 7 patients are alive and well and in complete clinical remission.

Thus we have shown that transfusion of transduced T-cells is effective and safe in a long follow-up of 11 years post transfusion.